Comparison of flocculated and dispersed single‐wall carbon nanotube‐based coatings using nonionic surfactants

Single‐wall carbon nanotubes (SWNTs) are promising filler materials for advanced polymer composites, but the impressive properties that have been predicted theoretically have not been realized experimentally. This gap is generally attributed to aggregation and nonideal dispersion of the SWNTs. Here, nonionic surfactants based on poly(ethylene oxide) are used to disperse SWNTs in either water or ethanol using sonication. The dispersed aqueous SWNTs are stable, while the analogous ethanol system yields loosely flocculated SWNTs. After drying these dispersions, the electrical conductivity of the flocculated system is at least an order of magnitude greater than the dispersed system at the same SWNT loading with conductivity greater than 20 S/cm obtained for the flocculated systems containing unsorted, commercial SWNTs. These flocculated systems can be readily sprayed to create conductive coatings. Despite their high electrical conductivity, these coatings provide only modest electromagnetic interference shielding (<20 dB) when testing large areas (30.5 × 30.5 cm²), which suggests significant heterogeneity or defects in these coatings that are not readily visible by eye or scanning electron microscopy. This defect mechanism is consistent with a decrease in shield efficacy at high SWNT loadings, despite no statistical change in the electrical conductivity of the coating. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers